1. Field of the Invention
The present invention relates to a process for controlling deployment of an air bag, comprising the steps of preparing a plurality of load sensors mounted in a seat of a vehicle and having an upper limit value in a detection range, detecting the weight of an occupant sitting on the seat as a total of outputs from the sensors, permitting the deployment of the air bag when the detected weight of the occupant is equal or larger than a predetermined value, and prohibiting the deployment of the air bag when the detected weight of the occupant is smaller than the predetermined value.
2. Description of the Related Art
The operation or non-operation of an air bag device for an assistant driver's seat, the deployment speed of an air bag and the like are controlled depending on the physical constitution and the presence or absence, i.e., the status of an occupant sitting on the assistant driver's seat. For example, if the occupant is an adult or a child, the air bag device is operated. If the occupant is a baby or infant sitting in a child seat (CRS), or if there is no occupant sitting on the seat, the air bag device is not operated. Further, even when the air bag device is operated, control is carried out such that if the occupant is an adult, the air bag is deployed at a high speed, and if the occupant is a child, the air bag is deployed at a low speed. Thus, it is possible to exhibit an optimal restraining performance corresponding to the status of the occupant by the air bag device, and to avoid unnecessary deployment of the air bag. The judgment of the status has been conventionally carried out based on the weight of an occupant detected by a load sensor mounted in the seat.
When the status is judged based on the weight of an occupant detected by the load sensor, the following standard is provided for the judgment, as shown in FIG. 6: for example, when the weight is equal to or larger than 50 kg, the status is determined to be “adult”; when the weight is equal to or larger than 20 kg and smaller than 50 kg, the status is determined to be “child”; when the weight is equal to or larger than 2 kg and smaller than 20 kg, the status is determined to be “child seat” (namely, a baby or infant); and if the weight is smaller than 2 kg, the status is determined to be “empty”. However, during traveling of a vehicle, not only a vertical acceleration due to the unevenness of a road surface is generated, but also a longitudinal acceleration due to an acceleration or deceleration and a lateral acceleration due to the turning of the vehicle are generated, so that the weight of the occupant detected by the load sensor mounted in the seat largely fluctuates, as shown in FIG. 6.
The output from the load sensor naturally changes depending on the vertical acceleration. The reason why the change in output from the load sensor depends on the longitudinal acceleration and the lateral acceleration is as follows: For example, when the vehicle is suddenly braked, an occupant sitting on the seat is thrown out forwards by an inertia, and hence a front portion of the seat is pushed against a floor, and a rear portion of the seat is lifted up from the floor. Therefore, when the load sensor is mounted at the front portion of the seat, a weight larger than an actual weight is detected; and when the load sensor is mounted at the rear portion of the seat, a weight smaller than the actual weight is detected. In the latter case, a negative weight may be detected.
To eliminate such disadvantages, it is conceived that a load sensor is mounted at each of four corners of the seat, and the status is judged from an average value or a total value of outputs from the four load sensors. However, such an output from each of the load sensors has an upper limit value and a lower limit value. The output over the upper limit value is modified to the upper limit value by a limiting process, and the output below the lower limit value is modified to the lower limit value by the limiting process. Therefore, when an adult or child is on the seat, there is a possibility that the air bag, which should be naturally deployed, is not deployed.
More specifically, when any one of the outputs from the four load sensors is modified to the upper limit value because it exceeds the upper limit value, an occupant's weight calculated from the average value or the total value of the outputs from the four load sensors is smaller than an actual weight. Therefore, there is a possibility that the status is erroneously judged as the child seat although the status is actually an adult or child, whereby the deployment of the air bag which should be naturally deployed is prohibited.